Power conservation in an image forming apparatus by delaying activation of a printing drum

ABSTRACT

A method for minimizing power consumption of a laser printer includes receiving page description language (PDL) data corresponding to a printing task, identifying commands corresponding to the received PDL data, computing a total predicted rendering time corresponding to the identified commands, computing a print deferral time according to the total predicted rendering time wherein the print deferral time corresponds to an amount of time by which printing drum initialization can be deferred without delaying completion of the printing task, and configuring a printing drum to begin operation according to the print deferral time. A computer program product and computer system corresponding to the method are also disclosed.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of laser printing,and more specifically to increasing efficiency in laser printing tasks.

Laser printing is an electrostatic digital printing process whichproduces texts and graphics by repeatedly passing a laser beam back andforth over a negatively charged cylindrical drum to define adifferentially-charged image. The drum then selectively collectselectrically charged powdered ink, or toner, and transfers the image topaper, which is then heated in order to permanently fuse the text and/orimagery. Laser printers receive data from a computer, and performrendering and drum printing on the received data.

SUMMARY

A method for minimizing power consumption of a laser printer includesreceiving page description language (PDL) data corresponding to aprinting task, identifying commands corresponding to the received PDLdata, computing a total predicted rendering time corresponding to theidentified commands, computing a print deferral time according to thetotal predicted rendering time wherein the print deferral timecorresponds to an amount of time by which printing drum initializationcan be deferred without delaying completion of the printing task, andconfiguring a printing drum to begin operation according to the printdeferral time. A computer program product and computer systemcorresponding to the method are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting one embodiment of a laser printingsystem in accordance with some embodiments of the present invention;

FIG. 2 is a flowchart depicting one embodiment of a drum initializationdelay method in accordance with some embodiments of the presentinvention;

FIG. 3A depicts a laser printing timeline before drum initialization isdeferred in accordance with one embodiment of the present invention;

FIG. 3B depicts a laser printing timeline after drum initialization isdeferred in accordance with one embodiment of the present invention; and

FIG. 4 depicts a block diagram of components of a computer, inaccordance with some embodiments of the present invention.

DETAILED DESCRIPTION

A printing drum and associated drum heater are energized only duringtimes of active printing (while paper is moving) and for a few secondsfor preheating. The power consumption of the drum and the heater arevery large, making it beneficial to minimize the amount of time forwhich the drum and the heater must be energized. Current laser printingmethods require the drum and heater to be operating during some periodswhen pages are not ready to be printed, which leads to unnecessarilylong operation times. The embodiments disclosed herein may enableminimization of a printing drum operation time.

FIG. 1 is a block diagram depicting one embodiment of a laser printingsystem 100 in accordance with some embodiments of the present invention.As depicted, laser printing system 100 includes a computer system 110, adata source 120, and a network 130. Laser printing system 100 maycorrespond to a system that can be made more efficient by a druminitialization delay method.

Computer system 110 can be a desktop computer, laptop computer,specialized computer server, or any other computer system known in theart. In some embodiments, computer system 110 represents a computersystem utilizing clustered computers and components to act as a singlepool of seamless resources when accessed through network 130. Ingeneral, computer system 110 is representative of any electronicdevices, or combination of electronic devices, capable of executingmachine-readable program instructions, as described in greater detailwith respect to FIG. 4.

As depicted, computer system 110 may include a printer driver 112.Printer driver 112 may be a piece of software that converts data to beprinted to a form specific to printer 120. Printer driver 112 enablesother applications on computing system 110 to carry out printing taskswithout being aware of the technical details of printer 120. In oneembodiment, printer driver 112 is configured to provide page descriptionlanguage data corresponding to a printing task to printer 120.

Printer 120 may be any peripheral which makes a persistent humanreadable representation of graphics or text on paper or similar physicalmedia. In some embodiments, printer 120 is a laser printer. Printer 120may be configured to receive a printing task from computer system 110via network 130. As depicted, printer 120 may include application 124.Application 124 may be configured to execute a drum initialization delaymethod to limit the power consumption corresponding to printer 120. Thedetails of the drum initialization delay method executed by application124 are described in greater detail with respect to FIG. 2. It should beappreciated that while FIG. 1 depicts application 124 as existing inprinter 120, in other embodiments of the present invention application124 could be hosted on a computer system instead.

Network 130 can be, for example, a local area network (LAN), a wide areanetwork (WAN) such as the Internet, or a combination of the two, andinclude wired, wireless, or fiber optic connections. In general, network130 can be any combination of connections and protocols that willsupport communications between computer system 110 and printer 120 inaccordance with an embodiment of the present invention.

FIG. 2 is a flowchart depicting one embodiment of a drum initializationdelay method 200 in accordance with some embodiments of the presentinvention. As depicted, drum initialization delay method 200 includesreceiving (210) page description language data corresponding to aprinting task, identifying (220) commands corresponding to the PDL data,computing (230) a total predicted rendering time of the commands,computing (240) a print deferral time, and configuring (250) a printingdrum to begin operation at the print deferral time. Drum initializationdelay method 200 may enable increased efficiency in laser printingtasks.

Receiving (210) page description language (PDL) data corresponding to aprinting task may include receiving PDL data from a printer driver. PDLdata is data that describes the appearance of a printed page on a higherlevel than an actual output bitmap. PDL data may be textual or binarydata streams. The received PDL data may include a plurality of fields,including a page number, color information, vector data, and image datacorresponding to the printing task. Receiving (210) PDL data may furtherinclude dividing the received PDL data based on which page itcorresponds to.

Identifying (220) commands corresponding to the PDL data may includeanalyzing the received PDL data to identify commands indicated by thePDL data. In one embodiment, identifying (220) commands comprisescreating a list of all commands indicated by the PDL data and the numberof occurrences of each command. The identified commands may be sortedaccording to the page to which they correspond.

Computing (230) a total predicted rendering time of the commands mayinclude comparing the list of commands to a correspondence table of PDLcommands and rendering times. The correspondence table may be a tablethat has been created in advance by applying PDL commands on a sampledata set with respect to the relevant printer and measuring therendering time associated with each command. For each identifiedcommand, a corresponding rendering time is identified within thecorrespondence table. The sum of the rendering times associated withcommands on a page of the printing task may be calculated to provide anestimated rendering time for each page.

Computing (240) a print deferral time may include calculating a time atwhich a printing drum should begin printing pages corresponding to theprinting task. The print deferral time may correspond to an amount oftime by which printing drum initialization could be delayed to minimizethe power consumption associated with the printing drum without delayingthe completion of the printing task. In one embodiment, the printdeferral time is applied with respect to an existing printing druminitialization time, which may correspond to the point at which thefirst page of the printing task has been rendered completely. The printdeferral time T may be calculated according to the equation:T=R ₂ +R ₃ + . . . +R _(N)−(D ₁ +D ₂ + . . . +D _(N-1))  (1)With respect to equation 1, R_(N) corresponds to a rendering timeassociated with an nth page of the printing task, D_(N) corresponds to adrum printing time associated with an nth page of the printing task, andN corresponds to the total number of pages in the printing task. In someembodiments, the drum printing time is constant for all pages regardlessof content, in which case the print deferral time T may be calculatedaccording to the simplified equation:T=R ₂ +R ₃ + . . . +R _(N)−(N−1)*D  (2)

Configuring (250) a printing drum to begin operation according the printdeferral time may include sending a signal to the printer to beginoperating at a point in time indicated by the print deferral time. Insome embodiments, the print deferral time is calculated with respect toan existing drum initialization time corresponding to the first page ofthe printing task being completely rendered. In these embodiments, theprinting drum initialization time to is calculated according to theequation:t ₀ =R ₁ +T  (3)

With respect to equation (3), R₁ corresponds to the time taken to renderthe first page of the printing task, and T corresponds to the printdeferral time as calculated according to equation (1) or equation (2).

FIG. 3A depicts a laser printing timeline 300A before druminitialization is delayed in accordance with one embodiment of thepresent invention. As depicted, laser printing timeline 300A includes astarting time 310, rendering times 320, print times 330, waiting times340, completion time 350, and printing drum engagement duration 360.Laser printing timeline 300A depicts the waiting times associated withinitializing a printing drum as soon as a first page of a printing taskhas rendered.

Starting time 310 corresponds to a point at which a printer beginsrendering a printing task. At starting point 310, the printer beginsrendering the first page, as indicated by rendering time 320A. Renderingtimes 320A, 320B, 320C, and 320D correspond to times associated withrendering pages 1, 2, 3, and 4, respectively. Similarly, print times330A, 330B, 330C, and 330D correspond to times associated withphysically printing pages 1, 2, 3, and 4, respectively.

Waiting times 340 correspond to periods of time during which theprinting drum remains active but is unable to begin printing a nextpage. As depicted, the printing time 330 associated with each page issignificantly shorter than the associated rendering time 320. For thisreason, once a page is finished printing, the printing drum is forced towait until a next page has finished rendering before it can beginprinting a next page. The drum must be kept revolving and heatedthroughout the duration of the printing task, and therefore remainsengaged during these wait times despite not being actively used.Completion time 350 corresponds to a point at which the printer hasfinished printing all pages associated with the printing task, and thepoint at which the printing drum is disengaged. Printing drum engagementduration 360 corresponds to the period of time during which the printingdrum is revolving and heated.

FIG. 3B depicts a laser printing timeline 300B after drum initializationis delayed in accordance with one embodiment of the present invention.Laser printing timeline 300B corresponds to the same printing task aslaser printing timeline 300A, except with respect to laser printingtimeline 300B, a printing drum initialization delay method has beenimplemented. As depicted, laser printing timeline 300B includes startingpoint 310 and completion point 350, indicating that the duration of theprinting job has not increased with the delay of the printing druminitialization. Laser printing timeline 300B also includes the samerendering times 320 as laser printing timeline 300A. However, asdepicted with respect to laser printing timeline 300B, a print deferraltime 370 has been introduced such that print time 330A doesn't occuruntil much later in the process. Deferring the printing in this mannerallows the four pages to be printed in immediate succession, leaving nounnecessary waiting time and therefore creating a shortened printingdrum engagement duration 380. With respect to the depicted embodiment,print deferral time 370 is calculated according to equation (2).

FIG. 4 depicts a block diagram of components of computer 400 inaccordance with an illustrative embodiment of the present invention. Itshould be appreciated that FIG. 4 provides only an illustration of oneimplementation and does not imply any limitations with regard to theenvironments in which different embodiments may be implemented. Manymodifications to the depicted environment may be made.

As depicted, the computer 400 includes communications fabric 402, whichprovides communications between computer processor(s) 404, memory 406,persistent storage 408, communications unit 412, and input/output (I/O)interface(s) 414. Communications fabric 402 can be implemented with anyarchitecture designed for passing data and/or control informationbetween processors (such as microprocessors, communications and networkprocessors, etc.), system memory, peripheral devices, and any otherhardware components within a system. For example, communications fabric402 can be implemented with one or more buses.

Memory 406 and persistent storage 408 are computer-readable storagemedia. In this embodiment, memory 406 includes random access memory(RAM) 416 and cache memory 418. In general, memory 406 can include anysuitable volatile or non-volatile computer-readable storage media.

One or more programs may be stored in persistent storage 408 for accessand/or execution by one or more of the respective computer processors404 via one or more memories of memory 406. In this embodiment,persistent storage 408 includes a magnetic hard disk drive.Alternatively, or in addition to a magnetic hard disk drive, persistentstorage 408 can include a solid state hard drive, a semiconductorstorage device, read-only memory (ROM), erasable programmable read-onlymemory (EPROM), flash memory, or any other computer-readable storagemedia that is capable of storing program instructions or digitalinformation.

The media used by persistent storage 408 may also be removable. Forexample, a removable hard drive may be used for persistent storage 408.Other examples include optical and magnetic disks, thumb drives, andsmart cards that are inserted into a drive for transfer onto anothercomputer-readable storage medium that is also part of persistent storage408.

Communications unit 412, in these examples, provides for communicationswith other data processing systems or devices. In these examples,communications unit 412 includes one or more network interface cards.Communications unit 412 may provide communications through the use ofeither or both physical and wireless communications links.

I/O interface(s) 414 allows for input and output of data with otherdevices that may be connected to computer 400. For example, I/Ointerface 414 may provide a connection to external devices 420 such as akeyboard, keypad, a touch screen, and/or some other suitable inputdevice. External devices 420 can also include portable computer-readablestorage media such as, for example, thumb drives, portable optical ormagnetic disks, and memory cards. Software and data used to practiceembodiments of the present invention can be stored on such portablecomputer-readable storage media and can be loaded onto persistentstorage 408 via I/O interface(s) 414. I/O interface(s) 414 also connectto a display 422.

Display 422 provides a mechanism to display data to a user and may be,for example, a computer monitor.

The programs described herein are identified based upon the applicationfor which they are implemented in a specific embodiment of theinvention. However, it should be appreciated that any particular programnomenclature herein is used merely for convenience, and thus theinvention should not be limited to use solely in any specificapplication identified and/or implied by such nomenclature.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The terminology used herein was chosen to best explain the principles ofthe embodiment, the practical application or technical improvement overtechnologies found in the marketplace, or to enable others of ordinaryskill in the art to understand the embodiments disclosed herein.

What is claimed is:
 1. A computer program product comprising: one ormore non-transitory computer readable storage media and programinstructions stored on the one or more computer readable storage media,the program instructions comprising instructions to: execute a set ofpossible commands in a printer rendering environment and calculating anaverage rendering time associated with each command of the set ofpossible commands to provide a rendering time table corresponding to theset of possible commands; receive page description language (PDL) datacorresponding to a printing task; identify commands corresponding to thereceived PDL data; compute a total predicted rendering timecorresponding to the identified commands by extracting rendering timescorresponding to the identified commands from a table indicating averagerendering times associated with PDL commands; compute a print deferraltime according to the equation: T=R₂+R₃+ . . . +R_(N)−(D₁+D₂+ . . .+D_(N-1)), wherein T corresponds to an amount of time by which aprinting drum initialization can be deferred without delaying completionof the printing task, R_(n) corresponds to a rendering time associatedwith an nth page of the printing task, D_(n) corresponds to a drumprinting time associated with an nth page of the printing task, and Ncorresponds to the total number of pages in the printing task; configurea printing drum to begin operation according to the print deferral time;and execute the received printing task according to the print deferraltime.